Am I in Labor....Not sure whats going on?

So im 37 weeks pregnant.....It feels like I need to poop about every 20 min or so but when I go to the rest room nothing happens and it goes away. My stomach has been getting tight with the braxton hick contractions a lot and every now and again I have dis comfort in my back. Yesterday i had massive diarrhea so I dont think Im constipated, it just worries me a little because my sister was induced with her first child and never felt one contraction. She had NO epidural or any type of pain meds. I know i just started my nesting thing bc I just cleaned my *** off. What could this be?